The assessment or determination of a degree of deformity of a knee joint or any other anatomical structure joining two limbs assist the planning and performing of surgery, alleviates possible complications, and fosters successful rehabilitation.
In cases of mild deformities of a knee joint, the knee joint is suitable for total knee arthroblasty (TKA), for instance.
Determination of structural anatomic features require the acquisition of locations and/or orientations of anatomic objects, such as limbs relative to a spatial coordinate system or operating space.
A locating or tracking device may be used to determine a pose (position and/or orientation) of an anatomical object in a three-dimensional coordinate system or operating space by means of an array of activated markers attached to the object. Herein, a position and/or orientation is an example for a pose. By receiving signals transmitted from the markers with a sensor or sensors in different poses (spatial positions and/or orientations) the pose (position and orientation) of the marker array and thus the pose (position and/or orientation) of the anatomical object to which the marker array is attached to may be determined.
An example of a system for tracking the spatial position and angular orientation of an object may be found in U.S. Pat. No. 5,828,770.
The pose (position and/or orientation) of an object in space is referred to as the pose of the object.
The following prior art documents are cited:                M. E. Nadzadi, M S; J. K. Nielsem, M S; S. B. Murphy, M D, smith and nephew Memphis, Tenn. Intact Knee Passive Kinematics and Ligamentous Stability Measured by a Novel Navigation System; and        M. E. Nadzadi, M S; J. K. Nielsern, M S; S. B. Murphy, M D, smith and nephew Memphis, Tenn. A Novel Method for Measuring Intact Knee Joint Laxity and Kinematics Using Computer Assisted Surgical Navigation Tools.        
An object of the present invention is to plan the placement of an implant in such a manner that movement of the joint after implantation corresponds to the movement of the replaced anatomical joint.
In particular, in case of a deformity of the anatomical joint to be replaced, the influence of a pre-operative deformity on the movement of the joint is preferably reduced due to the planning according to the invention.